The Blood Vessels Study Guide

Question 1

3 different types of blood vessels

Answer 1

Arteries
Capillaries
veins

Question 2

vessel that is the site of exchange between blood and interstitial fluid

Answer 2

capillaries

Question 3

what gets exchanged between blood and interstitial fluid at the capillaries?

Answer 3

O2, CO2, nutrients, waste, hormones

Question 4

Oxygenation levels of the blood within the various vessels of the pulmonary and systemic circuits

Answer 4

• Arteries = oxygen rich
• Veins = oxygen poor
  
  • Exceptions = Pulmonary Arteries (o2 poor), Pulmonary Veins (o2 rich), Umbilical Vessels (vein = o2 rich, artery = o2 poor)

Question 5

role of lymphatic vessels

Answer 5

Recovers fluid that leaks from blood vessels

Question 6

Tunica intima

Answer 6

contains endothelium - epithelium that lines all vessels and reduced friction (larger vessels have subendothelial layer supporting intima)

Question 7

Tunica media

Answer 7

circularly arranged smooth muscle cells and cheers of elastin

Question 8

Tunica externa

Answer 8

oosely woven collagen fibers that protect, reinforce, and anchor the vessel

Question 9

Vasa vasorum

Answer 9

a network of tiny blood vessels that nourish the vessel itself (found in tunica externa of larger vessels)

Question 10

Compare/contrast the anatomical structure of arteries and veins.

Answer 10

• Veins have valves, arteries do not
• Arteries have external elastic membrane around tunica media, veins do not
• Arteries have internal elastic membrane around tunica intima, veins do not

Question 11

What is the important functional role of the tunica media?

Answer 11

Vasoconstriction: smooth muscle contracts, and the lumen decreases
Vasodilation: smooth muscle relaxes, and the lumen increases
* Activity of the smooth muscle is regulated by sympathetic vasomotor nerve fibers and chemicals

Question 12

3 types of arteries

Answer 12

elastic
muscular
arterioles

Question 13

Elastic Arteries

Answer 13

“Conducting Arteries”
- Thick-walled arteries near the heart – aorta and its major branches
- Large diameters – 1 to 2.5cm
- Elastin present in all three tunics, but tunica media contains the most
- Despite smooth muscle, relatively inactive as vasoconstrictors
- Act as pressure reservoirs – expand/recoil as the heart ejects blood
- Elastic arteries “smooth” pressure and make blood flow fairly continuously – protection for smaller arteries

Question 14

Muscular Arteries

Answer 14

“Distributing Arteries”
- Distal to the elastic arteries
- Deliver blood to specific body tissues/organs
- Most named arteries are muscular arteries
- Ex: brachial, radial, common iliac, posterior tibial arteries
- Diameters range from the size of a pencil lead to a little finger
- Proportionate to their size, muscular arteries have the thickest tunica media
- More smooth muscle, less elastin tissue
- More active vasoconstrictors, less capable of stretch

Question 15

Arterioles

Answer 15

“Resistance Vessels”
- The smallest arteries, lumen size ranges 10µm to .3mm
- Larger arterioles have all three tunics - the tunica media is chiefly smooth muscle with minimal elastin
- Smaller arterioles are largely a single layer of smooth muscle around endothelial lining
- Diameter varies in response to neural, hormonal, and local chemical influences
- When arterioles constrict, the tissue is largely bypassed
- When arterioles dilate, blood flow into the local capillaries increases dramatically

Question 16

type of artery that has the highest percentage of tunica media (proportionate to its size)

Answer 16

Muscular arteries

Question 17

structure and function of a capillary bed

Answer 17

• Capillaries do not function independently – they form interweaving networks called capillary beds
• Blood flow through the capillary bed is controlled by the diameter of the terminal arteriole – this is altered by chemical conditions and vasomotor nerve fibers
• Secondary to changes in arteriole diameter, a capillary bed may be flooded with blood or it may be bypassed – important rerouting!

Question 18

tissues that do NOT have a rich capillary supply

Answer 18

tendons, ligaments, cartilage, and epithelia

Question 19

three types of capillaries

Answer 19

1. Continuous: most common, least permeable
2. Fenestrated: large fenestrations or pores increase permeability
3. Sinusoid: occur in limited locations, the most permeable

Question 20

continuous capillaries

Answer 20

• Abundant in skin, muscles, lungs, and the CNS
• The structural basis of the blood-brain barrier

Question 21

fenestrated capillaries

Answer 21

Abundant in kidneys, small intestine, and areas of hormone secretion

Question 22

Sinusoid capillaries

Answer 22

• Found in the liver, bone marrow, spleen, and adrenal medulla
• Have large intercellular clefts and irregular shapes
• Contain macrophages to catch prey

Question 23

intercellular cleft

Answer 23

• Gaps of un-joined membrane
• Intercellular Clefts allow limited passage of fluids and small solutes

Question 24

microcirculation

Answer 24

how blood flows from an arteriole to a venule through a capillary bed
- Gases, nutrients, hormones, and waste are exchanged during microcirculation

Question 25

postcapillary venule

Answer 25

The capillary bed drains into a postcapillary venule

Question 26

terminal arteriole

Answer 26

In most body regions, a terminal arteriole branches into 10 to 20 capillaries – the capillary bed
- Blood flow through the capillary bed is controlled by the diameter of the terminal arteriole – this is altered by chemical conditions and vasomotor nerve fibers

Question 27

process of rerouting blood including vascular shunt, metarteriole, and precapillary sphincter.

Answer 27

• Vascular Shunt: a vessel that directly connects the terminal arteriole to the postcapillary venule – allows blood to bypass the true capillaries
• Shunt consists of a metarteriole and a throughfare channel
• As true capillaries branch from the metarteriole, each is surrounded by a cuff of smooth muscle called a precapillary sphincter
• Precapillary sphincters act as valves to regulate blood flow into the capillaries – they are controlled by chemical conditions

Question 28

Venous Sinus

Answer 28

a highly specialized, flat vein with extremely thin walls (made of endothelium)

Question 29

Venules

Answer 29

• formed by uniting capillaries
• 8-100 µm in diameter
• Postcapillary venules are the smallest venules – they are made entirely of endothelium meaning they are porous and “leaky”
• Larger venules will have both tunicas media and externa

Question 30

Veins

Answer 30

• Venules merge to form veins
• Veins have all three tunics, but thinner walls and a larger lumen than arteries
• Veins have little elastin or smooth muscle in the tunica media
• The tunica externa is thick with longitudinal bundles of collagen
• !!!!!!Secondary to larger lumens, veins can act as blood reservoirs – they can hold up to 65% of the body’s blood supply at any given time
• Blood pressure in veins is much lower than in arteries – allowing for the veins’ thinner walls

Question 31

structural adaptations that improve blood’s ability to return to the heart via the veins

Answer 31

Large diameters to lower resistance, venous valves preventing backflow

Question 32

varicose veins

Answer 32

veins that are torturous and dilated secondary to incompetent/leaky valves

Question 33

anastomosis

Answer 33

special interconnection between blood vessels

Question 34

functional importance of anastomosis

Answer 34

Most organs receive arterial blood supply from more than one arterial branch. Found around joints, abdominal organs, heart, brain. If one pathway is lost, another can take over
(venous anastomoses, however rarely cause any problems)